Method for dispensing milk portions in drink preparation machines

ABSTRACT

The invention relates to a method for dispensing milk portions in drink preparation machines having a milk fill level monitoring unit for a milk container. According to the method, one delivery of a milk portion from the milk container, said delivery being controlled by a device control electronic system, is only carried out completely and with a sufficient quantity of milk when during the delivery of the milk portion, the milk fill level monitoring unit signals a drop in the fill level of the milk below a threshold value.

BACKGROUND

1. Field of the Invention

The invention relates to a method for dispensing milk portions in drinkpreparation machines having a milk fill level monitoring unit for a milkcontainer, such as coffee machines with a milk container provided forpreparing Capuccino. The invention further relates to a milk fill levelmonitoring unit for a milk container.

2. Description of Related Art

In coffee machines, producing the milk froth for the Capuccino and theheating of milk is carried out in many cases in a frothing device usingthe Venturi principle. A negative pressure is generated with a suitablesteam jet, which sucks the milk from the supply container (milkcontainer) via a hose system and guides it into the nozzle of thefrothing device. In the nozzle, the milk is brought together with thesteam and the milk-steam-air mixture leaves the frothing device and runsinto the cup through a steady outlet jet. If air is added to the coldmilk during the extraction, warm milk with a milk froth locatedthereover is produced in the cup. Without air being added, the milk canonly be heated.

If too little or no milk is present in the milk container and thesequence of the milk product deliveries, in particular the Capuccinodelivery in the coffee machine controller is fixedly programmed, theconsumer only receives a coffee without milk or with too little milk andmilk froth. For the user this is irksome since he must repeat the entireprocess once again to obtain a perfect Capuccino (milk product) andthrow away the coffee that has possibly already been withdrawn. Thismeans a waste of resources and also has financial implications,particularly if the consumer must pay a fixed amount for the Capuccinowithdrawal, whether this be in the office area or in the restaurantarea.

If the milk supply is interrupted, whether this be because no or toolittle milk is available, this does not form a homogeneous milk outletjet from the nozzle during withdrawal. In addition to the firstannoyance, there is the added factor that the front side of the coffeemachine can be contaminated by milk, water and steam splashes.

In addition, since in most cases the milk container is not transparent,it is difficult for the consumer to monitor the fill level of the milk.The supplied milk should be stored in a cooled manner as far aspossible. This is achieved in many cases with an insulating container(double-walled structure with an evacuated intermediate space) or with asmall refrigerator using a Peltier element. In these devices, it is notpossible to monitor the milk fill level without opening the container.In addition, this is also impractical in most cases and is frequentlyforgotten.

There are indeed drink preparation machines such as, for example, the“Thermoplan Tiger” from Thermoplan which have an integrated milk systemwith a cooled milk tank in the substructure. The device additionally hasa capacitively operating milk fill level monitoring unit. Naturallyhowever, the milk fill level in the milk tank is not readily apparent tothe user of the drink preparation machine even in this case. It hasadditionally been found that in the event of the milk fill levelmonitoring unit being tripped, i.e. in the event of the capacitivelyoperating sensor being tripped in this device, a milk dispensing processwhich is possibly just being executed, is not carried out completely butis prematurely interrupted.

Known from WO 97/47376 is a frothing apparatus for milk in which milkcan be extracted from a milk container via a suction tube by means of apump under the control of a microprocessor controller and can be fed toa mixing device in which the extracted milk can be mixed with steam andair and can be frothed in this manner. This frothing apparatus comprisesa sensor for determining the fill level in the milk container, whichsensor is disposed relative to the bottom of the milk container at thesame level as a suction opening for extracting the milk, which suctionopening is disposed at the lower end of the suction tube, whereinsignals from the sensor can be received by the microprocessorcontroller.

SUMMARY OF VARIOUS EMBODIMENTS

It is thus the object of the invention to provide an improved and moreuser-friendly method for preparing drinks with milk or milk constituentsin drink preparation machines such as coffee machines. Furthermore, asuitable milk fill level monitoring unit will be provided for carryingout the method.

This object is achieved by the features of claims 1 and 2.

The solution starts from the fact that a delivery of a milk portion fromthe milk container, controlled by the electronic device control system,is carried out completely and with a sufficient quantity of milk evenwhen, during a delivery of the milk portion, the milk fill levelmonitoring unit signals a drop in the fill level of the milk below athreshold value.

At the same time, in order to further increase the user friendliness ofthe drink preparation machine, when the fill level of the milk dropsbelow the threshold value, the user is given an indication on a displaythat the milk container is empty and further deliveries of milk portionsare blocked until the milk container is sufficiently filled again or atleast until the milk fill level monitoring unit releases this functionagain.

By ensuring that a milk delivery process, once initiated, is alwayscompleted, it is achieved that the milk outlet jet always remainshomogeneous and as a result jet irregularities and splashes are reliablyavoided.

Naturally, the necessary conditions for this must also be provided onthe hardware side. Thus, it must be ensured by constructive measuresthat in the event of the threshold value sensor being tripped, there isstill sufficient milk in the milk container to actually complete theinitiated process. However, since such measures are substantiallyquestions of dimensioning in most cases, e.g. by specifying the heightof the suction opening of a suction tube and the level of triggering ofa threshold value signal, in the exemplary embodiment shown, referenceis merely made to one possible embodiment.

Various principles of action can be used in the threshold value sensors.Thus, for example, sensors using the capacitive or resistive principlescan be used. Capacitive monitoring has the advantage that this issimpler to achieve electronically. However, such circuits arefundamentally known to the person skilled in the art which is why theyare not explained in detail in the following.

Due to the possibility that either an internally or an externallydisposed milk container can be used, the user friendliness can befurther improved, in particular if a modular extension concept isprovided (i.e. a suitable milk container can be made available to thedrink preparation machine).

In the case of an externally disposed milk container, an externalelectronic evaluation system attached to the milk container can also beprovided. However, this is usually only used for fill level informationand with the exception of signal relaying functions, has no furtherfunctions on the electronic device control system of the drinkpreparation machine. However, it can nevertheless be very practical andconducive to clarity to display the fill level directly on the‘affected’ device.

The fill level monitoring according to the invention in a coffee machinewill be explained in detail hereinafter for two examples using theresistively acting sensor principle with reference to drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

In the drawings:

FIG. 1 shows a schematic diagram of a coffee machine with a milkcontainer provided,

FIG. 2 shows a sectional drawing of the milk container with an externalelectronic evaluation system in a first embodiment and

FIG. 3 shows a simplified sectional drawing of the arrangement of theelements of the milk fill level monitoring unit in the milk containeraccording to the first embodiment.

FIG. 4 shows a sectional drawing of the milk container with an externalelectronic evaluation system in a second embodiment.

DETAILED DESCRIPTION

FIG. 1 shows a schematic diagram of a coffee machine with a milkcontainer 1 provided.

In this case, milk is poured into the milk container 1 which is locatedin a coffee machine 11 or preferably outside said coffee machine. Thisliquid container 1 is preferably an insulating container and can be madeof metal, glass or plastic. As a result, the milk can be stored for sometime in this container. The milk is sucked by a suction tube 3 with aflexible hose 7 to a milk frother 12 with a milk outlet 13. On one sidethe hose 7 is plugged onto a hose connection 6 of a container lid 2 ofthe milk container 1 and on the other side it is plugged onto a dockingpoint 8 of the milk frother 12. Both connections can be removed by theuser for cleaning.

The suction tube 3 and a measuring rod 4 are fastened on the containerlid 2 at a suitable distance with respect to one another. The suctiontube 3 is required for extracting the milk and is made of anelectrically conductive material, preferably metal. The shorter,likewise electrically conductive measuring rod 4, which can also beimplemented as a tube closed at the bottom, is fixed parallel to thesuction tube 3 on the container lid 2. A temperature measurement canalso be integrated in the measuring rod 4 by which means the milktemperature can be measured or monitored. If the temperature is toohigh, this can be notified to the consumer directly via a display 10 onthe coffee machine 11. The two elements suction tube 3 and measuring rod4 are connected electrically to an electronic device control system 9 ofthe coffee machine 11 by means of a signal line 5. The fill level of themilk can be monitored by means of variation in conductance between thesuction tube 3 and the measuring rod 4. The conductivity of the milk ishigher than that of air. The principle can also be applied to otherliquids such as water, tea, etc. If the milk level falls below the(shorter) measuring rod 4, there is a marked jump in the measurementsignal. This signal is evaluated directly in the electronic devicecontrol system 9 or evaluated with an external display 16. When thesignal evaluation is made directly by the electronic device controlsystem 9, the delivery of milk products can be interrupted or blockeduntil sufficient milk has been topped up again. This ensures that theoutlet jet from the milk outlet 13 of the milk frother 12 always remainshomogeneous.

The electronic device control system 9 can also release a certainfollow-up quantity 14 so that the actuated delivery is not interruptedif the set milk delivery quantity does not exceed a residual quantity 15in the milk container 1. The request for topping up the milk is onlymade at the end of the milk delivery. The fill level minimum (alarm) canbe notified to the consumer with various possibilities for display; itcan be accomplished visually by means of a display indication, aluminous LED or pictogram or the like or it can be effected audibly bymeans of a beeper, buzzer, vibrator or the like.

The applied measurement principle also functions when the suction tube 3and the measuring rod 4 are arranged coaxially.

If the milk container 1 is made of metal, the fill level monitoring canalso be made between the container wall and the measuring rod 4 and thesuction tube 3 could then be made of a non-conducting material. Thecorresponding signal line 5 must then naturally not be secured to thesuction tube 3 but to the container wall of the milk container 1.

FIG. 2 shows a sectional drawing of the milk container 1 with anexternal electronic evaluation system 16 in a first embodiment. In thiscase, the measurement signal from the threshold value sensor is notconnected directly to the electronic device control system 9 of thedrink preparation machine but is fed to the external electronicevaluation system 16. When the signal evaluation is made with anexternal electronic evaluation system 16, the product delivery is notprevented but merely indicated when the fill level is fallen below orthe liquid container 1 is empty. If the display 10 on the externalelectronic evaluation system 16 is not noted by the consumer and aCapuccino delivery is triggered nevertheless, the jet from the milkoutlet 13 is not homogeneous when the fill level is fallen below. Thefill level minimum can be displayed to the consumer with similar meansas on the drink preparation machine.

FIG. 3 shows another simplified sectional drawing of the arrangement ofthe elements of the milk fill level monitoring unit in the milkcontainer according to the first embodiment. The suction tube 3 projectsdeeper into the milk container 1 than the shorter measuring rod 4. Ifthe fill level falls below the level A, the lower end of the measuringrod 4 no longer touches the milk and the measured conductance betweenthe suction tube 3 and the measuring rod 4 is then much lower. In thisexemplary embodiment, the level A therefore designates the mentionedthreshold value. Nevertheless, milk can be further extracted via thesuction tube 3 until the suction opening 17 of the suction tube isexposed (indicated as level B) and only a residual quantity 15 remainsin the milk container. The amount of milk which can be extracted betweenlevel A and B is designated as the follow-up quantity 14 and isdetermined in such a manner that when the method according to theinvention is being used to deliver milk portions, the delivery of milkportions can always be completed. The follow-up quantity 14 is thereforethe same as or greater than the largest amount of milk required perdrink selection.

FIG. 4 finally shows a sectional drawing of the milk container with anexternal electronic evaluation system in a second embodiment. In thiscase, the milk container 1 is made of metal (or an electricallyconductive material). Thus, the fill level monitoring can also be madedirectly between the milk container 1 and the suction tube 3. This is amore cost-effective solution. In this case, the suction tube 3 must beconstructed of two materials. The upper part of the suction tube 3 ishere made of an electrically conductive material (preferably metaltube), the lower part, in this case a suction part 19, is made of anon-conductive material (preferably plastic or rubber). Both parts mustbe tightly connected to one another. The signal lines 5 are connected bymeans of a contact spring 18 and a conducting connecting piece.

The evaluation signal is generated by measuring the conductivity betweenthe suction tube 3 and the milk container 1. For this purpose, the upperend of the suction tube 3 and the milk container 1 are electricallyconnected to the external electronic evaluation system 16. If the milklevel drops below the electrically conducting part of the suction tube,a marked jump in the measurement signal takes place, However, thesuction part 19 can still extract milk from the milk container 1. Thelength of the non-conducting suction part 19 determines the residualquantity 15 and the follow-up quantity 14 in the milk container 1.

1. A method for dispensing milk portions in drink preparation machineshaving a milk fill level monitoring unit for a milk container, whereinaccording to the method a delivery of a milk portion from the milkcontainer controlled by a device control electronic system is carriedout completely and with sufficient quantity of milk even when the milkfill level monitoring unit signals a drop in the fill level of the milkbelow a threshold value during the delivery of the milk portion, whenthe fill level of the milk drops below the threshold value, the user ofthe drink preparation machine is given an indication on a display thatthe milk container is empty and further deliveries of milk portions tothe drink preparation machine are blocked until the milk container issufficiently refilled or at least until the milk fill level monitoringunit releases this function again.
 2. A drink preparation machinecomprising a milk container and a milk fill level monitoring unit forcarrying out the method according to claim 1, wherein the drinkpreparation machine has an electronic device control system, a displayand a milk frother and wherein a suction tube of the milk container isconnected via a tube or hose to the milk frother and wherein the suctiontube dipping into the milk container has a suction opening and ameasuring rod likewise dipping into the milk container to form a hethreshold value and a capacitively or resistively operating thresholdvalue sensor is provided, characterised in that the suction opening isdisposed at the lower end of the suction tube closer to the bottom ofthe milk container than a lower end of the measuring rod and a verticaldistance between the suction opening on the suction tube and the lowerend of the measuring rod is arranged in such a manner that, when thefill level of the milk drops below the threshold value, a minimalpredetermined residual volume of milk can still be extracted.
 3. A drinkpreparation machine comprising a milk container and a milk fill levelmonitoring unit for carrying out the method according to claim 1,wherein the drink preparation machine has an electronic device controlsystem, a display and a milk frother and wherein a suction tube of themilk container is connected via a tube or hose to the milk frother andwherein the suction tube dipping into the milk container has a suctionopening and at the same time serves as a measuring rod dipping into themilk container to form a threshold value and a capacitively orresistively operating threshold value sensor is further provided,characterised in that the suction tube and the milk container areelectrically conducting and an electrically non-conducting suction partis placed at the lower end of the suction tube and the height of thenon-conducting suction part is dimensioned so that when the fill levelof the milk drops below the threshold value, a minimal predeterminedresidual volume of milk can still be extracted.
 4. The drink preparationmachine according to claim 2 or 3, characterised in that when a milkcontainer is located externally with respect to the drink preparationmachine, an external electronic evaluation system attached to the milkcontainer is provided.